System and method for multiple step directional patterning

ABSTRACT

A semiconductor process system includes an ion source configured to bombard with a photoresist structure on a wafer. The semiconductor process system reduces a width of the photoresist structure by bombarding the photoresist structure with ions in multiple distinct ion bombardment steps having different characteristics.

BACKGROUND Technical Field

The present disclosure relates to the field of semiconductor processing.The present disclosure relates more particularly to patterning featureson semiconductor wafers.

Description of the Related Art

There has been a continuous demand for increasing computing power inelectronic devices including smart phones, tablets, desktop computers,laptop computers and many other kinds of electronic devices. One way toincrease computing power in integrated circuits is to increase thenumber of transistors and other integrated circuit features that can beincluded for a given area of semiconductor substrate.

To continue decreasing the size of features in integrated circuits,various thin-film deposition techniques, etching techniques, and otherprocessing techniques are implemented. Many etching processes involvedepositing a layer of photoresist and patterning the photoresist byexposing the photoresist to ultraviolet light through a photolithographymask. The mask includes the pattern to be formed in the photoresist.However, as the size of desired features decreases, it can be difficultto pattern the photoresist in the desired manner.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying Figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is an illustration of a semiconductor process system, accordingto one embodiment.

FIGS. 2A-2K are cross-sectional views of a wafer, according to oneembodiment.

FIG. 2K is a top view of the wafer of FIG. 2A, according to oneembodiment.

FIG. 2L is a top view of the wafer of FIG. 2H, according to oneembodiment.

FIG. 3 is a graph illustrating changes in photoresist width for variousion bombardment characteristics, according to one embodiment.

FIGS. 4A-4D are top views of wafers, according to one embodiment.

FIGS. 5A-5D are top views of wafers, according to one embodiment.

FIG. 7 is a block diagram of a control system, according to oneembodiment.

FIG. 8 is a flow diagram of a method for processing a wafer, accordingto one embodiment.

FIG. 9 is a flow diagram of a method for processing a wafer, accordingto one embodiment.

DETAILED DESCRIPTION

In the following description, many thicknesses and materials aredescribed for various layers and structures within an integrated circuitdie. Specific dimensions and materials are given by way of example forvarious embodiments. Those of skill in the art will recognize, in lightof the present disclosure, that other dimensions and materials can beused in many cases without departing from the scope of the presentdisclosure.

The following disclosure provides many different embodiments, orexamples, for implementing different features of the described subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present description. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the Figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe Figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various embodiments of thedisclosure. However, one skilled in the art will understand that thedisclosure may be practiced without these specific details. In otherinstances, well-known structures associated with electronic componentsand fabrication techniques have not been described in detail to avoidunnecessarily obscuring the descriptions of the embodiments of thepresent disclosure.

Unless the context requires otherwise, throughout the specification andclaims that follow, the word “comprise” and variations thereof, such as“comprises” and “comprising,” are to be construed in an open, inclusivesense, that is, as “including, but not limited to.”

The use of ordinals such as first, second and third does not necessarilyimply a ranked sense of order, but rather may only distinguish betweenmultiple instances of an act or structure.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment. Thus, the appearances of the phrases “in some embodiments”or “in an embodiment” in various places throughout this specificationare not necessarily all referring to the same embodiment. Furthermore,the particular features, structures, or characteristics may be combinedin any suitable manner in one or more embodiments.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contentclearly dictates otherwise. It should also be noted that the term “or”is generally employed in its sense including “and/or” unless the contentclearly dictates otherwise.

Embodiments of the present disclosure decrease the size of photoresiststructures after initial patterning of the photoresist. Photoresist isinitially deposited on a wafer and patterned by exposure to lightthrough a mask. This initial patterning process forms trenches orapertures in the photoresist. The remaining photoresist separates thetrenches or apertures. After initial patterning, the lateral dimensionsof the remaining photoresist structures may be greater than desired.Embodiments of the present disclosure reduce the lateral dimensions ofthe remaining photoresist by removing a portion of the remainingphotoresist with multiple steps of directional ion bombardment. Themultiple steps of directional ion bombardment reduce the lateraldimensions of remaining photoresist structures and correspondinglyincrease the width of trenches or apertures. This is highly beneficialbecause structures can be formed closer together.

FIG. 1 is a simplified illustration of a semiconductor process system100, according to one embodiment. The semiconductor process systemincludes a process chamber 102. A wafer support 104 is positioned in theprocess chamber 102. The wafer support 104 supports a wafer 106 in theprocess chamber 102. An ion source 108 is positioned in the processchamber 102. As will be set forth in greater detail below, thecomponents of the semiconductor process system 100 cooperate to patternphotoresist on the wafer 106 via multiple steps of ion bombardment.

FIG. 1 illustrates a single process chamber 102. However, as will be setforth in more detail below, it is possible that some of the processesdescribed below may be performed in different process chambers.

The semiconductor process system 100 includes semiconductor processequipment 110. The semiconductor process equipment 110 assists inperforming semiconductor processes. The semiconductor process equipment110 can include equipment that assists in photolithography processes.For example, the semiconductor process equipment 110 can includeequipment for depositing a layer of photoresist on the wafer 106. Thesemiconductor process equipment 110 can include equipment for performingan initial patterning of the photoresist. Accordingly, the semiconductorprocess equipment 110 can include photolithography masks, ultravioletlight generation equipment, and associated optical equipment fordirecting ultraviolet light onto the photoresist layer.

The process equipment can include equipment for performing thin-filmdeposition processes, etching processes, ion implantation processes,annealing processes, photolithography processes, and other types ofprocesses. Some of the semiconductor process equipment 110 may bepositioned partially within the process chamber 102 and partiallyexternal to the process chamber 102. Some of the semiconductor processequipment 110 may be positioned entirely external to the process chamber102.

The semiconductor process equipment 110 can include equipment formanaging fluid flow within the process chamber 102. The processequipment can include components for introducing gasses or fluids intothe process chamber 102, for removing gasses or fluids from the processchamber, and for monitoring and controlling the flow, presence, orcomposition of gasses within the process chamber 102. The semiconductorprocess equipment 110 can include equipment for retaining a selectedpressure within the interior of the process chamber 102.

The semiconductor process equipment 110 can include electricalcomponents for generating electric fields, voltages, magnetic fields,electrical signals, or other types of electrical effects. Accordingly,the semiconductor process equipment 110 can include electrodes, wires,radiofrequency power sources, transmitters, receivers, or other types ofelectrical equipment that may be utilized in semiconductor processes.

The semiconductor process equipment 110 is utilized to deposit a layerof photoresist on the wafer 106. After the layer of photoresist has beendeposited on the wafer 106, the semiconductor process equipment 110performs an initial patterning of the photoresist. The initialpatterning forms trenches or apertures in the photoresist in accordancewith the pattern of a photolithography mask. In particular, thephotoresist is exposed to light via the mask, thereby changing thestructure of the photoresist that is exposed to light. The portion ofthe photoresist that is not exposed to light due to the presence of themask does not undergo structural change. The initial patterning processincludes removing either the portion of the photoresist that was changedby exposure to the light, or the portion of the photoresist that was notchanged by exposure to light, depending on the type of photoresist andphotolithography process utilized. The removal of the photoresist afterexposure results in the initial pattern of trenches and apertures in thephotoresist.

Due to limitations of photolithography processes, it is possible thatthe remaining photoresist structures that define the trenches andapertures have one or more lateral dimensions that are wider thandesired. As used herein, lateral dimensions correspond to X and Ydimensions that are mutually orthogonal to each other and to the Zdimension that corresponds to the vertical thickness of the photoresist.Accordingly, the lateral width of some of the remaining photoresiststructures may be larger than desired due to limitations ofphotolithography processes.

The system 100 utilizes the ion source 108 to reduce a lateral width ofremaining portions of the photoresist after initial patterning. The ionsource 108 outputs an ion beam including toward the wafer 106 at aselected angle relative to vertical. The ions bombard or impact thephotoresist. The impact of the ions on the remaining photoresiststructures removes a portion of the remaining photoresist structures.This reduces the lateral width of the remaining photoresist structures.This reduction in lateral photoresist dimensions by directional ionbombardment may be termed a directional push.

The ion source 108 bombards the photoresist structures with ions inmultiple steps. In a first ion bombardment step, the ions travel with anangle relative to vertical, have an energy, and a dose level. In asecond subsequent ion bombardment step, one or more aspects of the ionbeam is changed from the first ion bombardment step. Accordingly, in thesecond ion bombardment step, one or more of the angle of travel, theenergy, or the dose level of the ion beam is changed from the first ionbombardment step. The two ion bombardment steps with differentcharacteristics result in a more effective reduction in width of theremaining photoresist features than if only a single ion bombardmentstep is performed or if the second ion bombardment step was identical tothe first ion bombardment step.

In one embodiment, in the first ion bombardment step the ions are outputtoward the wafer 106 with a first angle relative to vertical. In thesecond subsequent ion bombardment step, the ions are output toward thewafer 106 with a second angle different than the first angle. Thiscombination of different ion bombardment angles reduces the effects ofshadowing and results in effective removal of photoresist. Shadowing canreduce the effectiveness of the ion bombardment processes. Furtherdetails regarding shadowing are set forth in relation to FIGS. 2A-2L.

In one embodiment, in the first ion bombardment step the ions are outputtoward the wafer 106 with a first energy. In the second subsequent ionbombardment step, the ions are output toward the wafer 106 with a secondenergy different than the first energy. This combination of differention bombardment energies reduces hardening and results in effectivephotoresist removal. The energy of an ion corresponds to its kineticenergy. For two ions of the same mass, the ion with more energy willhave a higher velocity than the ion with less energy.

In one embodiment, in the first ion bombardment step a first dose ofions are output from the ion source 108 to the wafer 106. In the secondsubsequent ion bombardment step, a second dose of ions different thanthe first dose are output from the ion source 108 to the wafer 106. Asused herein, a dose corresponds to the number of ions that bombard thewafer 106 in a given ion bombardment step. A higher ion bombardment dosecorresponds to a greater number of ions bombarding the wafer 106. If thenumber of ions per second is constant for two ion bombardment steps,then a higher dose can correspond to bombarding the wafer 106 for alonger period of time.

In practice, the two ion bombardment steps will be performed for eachside of a photoresist structure. If a photoresist structure isconsidered as a vertical wall having two vertical sides and a topsurface, then in one embodiment the two ion bombardment steps will beperformed first on one vertical side and then on the other verticalside. Accordingly, after the two ion bombardment steps have beenperformed on the first vertical side, then the two ion bombardment stepswill be performed on the second vertical side. To accomplish this, thewafer 106 is rotated 180° in the X-Y plane after the first two ionbombardment steps. The second two ion bombardment steps are thenperformed after the rotation. In one embodiment, the first ionbombardment step is first performed on a first vertical side of aphotoresist structure. The wafer is then rotated 180° in the X-Y planeand the first ion bombardment step is then performed on the secondvertical side of the photoresist structure. The second ion bombardmentstep is then performed on the second vertical side of the photoresiststructure. The wafer is then rotated 180° in the X-Y plane and thesecond ion bombardment step is performed on the first vertical side ofthe photoresist structure.

The system 100 includes a control system 112. The control system 112 iscoupled to the ion source 108. The control system 112 sends commands tothe ion source 108 to control the parameters of ion bombardment.Accordingly, the control system 112 can control the ion source 108 tooutput ions with a selected angle, a selected energy, and a selecteddose. The control system 112 controls the ion source 108 to change oneor more of these parameters from the first ion bombardment step to thesecond ion bombardment step.

The control system 112 may also be coupled to the process equipment 110.The control system 112 can control the function of the process equipment110. The control system 112 may also be coupled to the support 104. Thecontrol system 112 may control rotation of the support 104. Inparticular, after the first and second ion bombardment step have beenperformed on a first side of a photoresist feature, the control system112 can cause the support 104 to rotate the wafer 106 180°. The controlsystem 112 can then cause the ion source 108 to perform the first andsecond ion bombardment steps on the second side of the photoresistfeature. Alternatively, the system 100 can include a robot arm or othermechanisms for rotating the wafer 106 between sets of ion bombardmentsteps. The control system 112 can control the robot arm or othermechanisms.

FIG. 2A is a cross-sectional view of a wafer 106 at an intermediatestage of processing, according to one embodiment. The wafer includes asubstrate 122 and photoresist structures 120 on the substrate 122. Thesubstrate 122 can include a dielectric layer, a conductive layer, asemiconductor layer, or other type of material. In one example, thesubstrate 122 is an interlevel dielectric layer such as silicon oxide,silicon nitride, or other suitable dielectric materials.

The photoresist structures 120 are remnants of a photoresist layer thathas been patterned with an initial patterning process. The initialpatterning process can include standard photolithography patterning suchas exposure to ultraviolet light to a mask, and removal of exposed orunexposed photoresist.

The photoresist structures 120 each include a first side 124, a secondside 126, and a top surface. The photoresist structures can beconsidered photoresist walls. The photoresist structures each have awidth W1. The initial patterning process defines trenches 128 betweenadjacent photoresist structures 120. The trenches 128 each have a widthW2 between adjacent photoresist structures. FIG. 2A illustrates that theX dimension is the lateral dimension between adjacent photoresiststructures 120. FIG. 2A illustrates that the Z dimension is the verticaldimension. The top views of FIGS. 2K and 2L illustrates that the Ydimension is the lateral dimension perpendicular to the X dimension andthe Z dimension. In the view of FIG. 2A, the Y dimension corresponds tothe dimension into and out of the sheet.

In some cases, it is desirable to decrease the width W1 of thephotoresist structures 120. This can correspond to widening the trenches128. As described previously, standard photolithography processes maynot be able to produce photoresist structures 120 with lateraldimensions as small as desired.

One solution to reduce the width of the photoresist structures 120 is tobombard them with ions. In order to reduce the lateral dimension, thewalls 124 and 126 can be bombarded with the ions. In order to bombardthe walls 124 and 126 with ions, the ions will travel at an anglerelative to vertical. However, bombarding the sidewalls 124 and 126 atan angle presents some difficulties. If the angle is too great relativeto vertical, then the ions will be blocked from hitting the lower partsof the side wall 124 or 126 of the photoresist structure 120 by anadjacent photoresist structure 120. Thus, material will only be removedfrom an upper portion of the wall 124 or 126. This issue is known asshadowing. If the ion bombardment angle is reduced such that ions canimpact the entire wall 124 or 126, less photoresist material is removedbecause fewer ions per surface area impact the wall. Furthermore, ionbeams can produce a hardening effect on the sides 124 and 126 of thephotoresist structures 120. The hardening of the photoresist results inless material being removed.

Embodiments of the present disclosure overcome or reduce the effects ofhardening or shadowing by performing ion bombardment on each side 124and 126 in two separate ion bombardment steps. One or morecharacteristics of the ion bombardment is changed between the first stepand the second step. Some of the characteristics that can be changedinclude bombardment angle, ion energy, and dose level. FIGS. 2B-2Hillustrate a change in bombardment angle between the first bombardmentstep and the second bombardment step. However, as will be set forth inmore detail below, other characteristics aside from or in addition tobombardment angle can be changed between the first bombardment step andthe second bombardment step.

FIG. 2B illustrates a first ion bombardment step of the first sides 124of the photoresist structures 120. This can also be consideredbombardment of the first sides of the trenches 128. Ions 129 are emittedfrom the ion source 108 (see FIG. 1). The ions 129 travel at an angle θ₁with respect to vertical. As can be seen in FIG. 2B, the ions 129 impactthe upper portions of the sides 124 but do not impact the lower portionsof the sides 124. This is because of the shadowing effect describedpreviously. In particular, the ions 129 that would impact the lowerportions of the sides 124 are blocked from doing so by the adjacentphotoresist structure 120. The larger the angle θ₁ is relative tovertical, the smaller will be the portions of the sides 124 that areimpacted by ions 129. Nevertheless, it is beneficial to perform a firstion bombardment step at the first angle θ₁ to bombard upper portions ofthe sides 124. In one embodiment, the ions 129 are argon ions. However,the ions 129 can be other types of ions without departing from the scopeof the present closure.

In one embodiment, the first angle θ₁ is between 55° and 65° relative tovertical. If the angle θ₁ is above this range, then an insufficientupper portion of the walls 124 may be impacted by ions 129 for the firstbombardment step. If the angle θ₁ is lower than this range, then aninsufficient number of ions per unit area may impact the walls 124 forthe first ion bombardment step. In one example, the angle θ₁ is 60°.Other angles for 81 can be utilized without departing from the scope ofthe present disclosure.

FIG. 2C illustrates the wafer 106 after the first ion bombardment stepof the sides 124 of the photoresist structures 120. As can be seen,photoresist material has been removed from the upper portions of thesides 124 of the photoresist structures 120. No material has beenremoved from the lower portions of the sides 124 of the photoresiststructures 120.

FIG. 2D illustrates a second ion bombardment step of the first sides 124of the photoresist structures 120, or of the first sides of the trenches128. The ion source 108 outputs the ions 129 at a second angle 82relative to vertical. The angle 82 is different than the first angle θ₁.The angle 82 is smaller than the angle θ₁ relative to vertical. Theangle 82 is selected so that ions 129 impact the entirety of the sides124 of the photoresist structures 120. In the second ion bombardmentstep there is no shadowing effect.

In one embodiment, the second angle 82 is between 40° and 50° relativeto vertical. If the angle 82 is above this range, then shadowing mayoccur and the photoresist material will not be removed from the lowerportions of the sides 124. If the angle 82 is lower than this range,then an insufficient number of ions per unit area may impact the walls124 for the second ion bombardment step. In one example, the angle 82 is45°. Other angles for 82 can be utilized without departing from thescope of the present disclosure.

FIG. 2E illustrates the wafer 106 after the second ion bombardment stepof the sides 124 of the photoresist structures 120. As can be seen,photoresist material has been removed from both the lower portions andthe upper portions of the sides 124 of the photoresist structures 120.Using the high incident angle in the first ion bombardment step resultsin a slope on the sides 124 just above the lower part of the sides 124.This slope makes the second, low incident angle ion bombardment stepmore effective because the ions hit the sloped portion at an anglecloser to normal. Accordingly, the combination of the high incidentangle first bombardment step and the low incident angle secondbombardment step effectively removes material from the sides 124 of thephotoresist structures 120. The combination of the high incident anglefirst ion bombardment step and low incident angle second bombardmentstep reduces the effect of shadowing and effectively removes thephotoresist.

In FIG. 2F, the wafer 106 has been rotated 180° in the X-Y plane. Theresult is that the sides 126 of the photoresist structures 120 areexposed to the ion source 108 (see FIG. 1). In FIG. 2F, the first ionbombardment step is performed on the sides 126 of the photoresiststructures 120. This corresponds to performing a first ion bombardmentstep on the second sides of the trenches 128. The ions 129 are outputfrom the ion source 108 at the first angle θ₁. In other words, the firstion bombardment step of the side 126 shown in FIG. 2F is substantiallythe same as the first ion bombardment step of the side 124 asillustrated in FIG. 2B. One potential difference is that a smallerportion of the side 126 may be affected by shadowing due to the removalof material from the first side 124 as described previously. The firstion bombardment step of the sides 126 results in removal of photoresistmaterial from upper portions of the sides 126, as can be seen in FIG.2G.

In FIG. 2G, the second ion bombardment step is performed on the sides120 the photoresist structures 120. This corresponds to performing asecond ion bombardment step in the second sides of the trenches 128. Theions 129 are output from the ion source 108 at the second angle 82. Inother words, the second ion bombardment step of the side 126 shown inFIG. 2G is substantially the same as the second ion bombardment step ofthe side 124 as illustrated in FIG. 2D. The second ion bombardment stepof the sides 126 results in removal of photoresist material from boththe upper and lower portions of the sides 126.

FIG. 2H illustrates the wafer 106 after the first and second ionbombardment steps have been performed on the sides 124 and 126 of thephotoresist structures 120. A significant amount of photoresist materialhas been removed from both sides 124 and 126 of each of the resiststructure 120. This corresponds to reducing the lateral width of thephotoresist structures 120 in comparison to the photoresist structures120 in FIG. 2A. The width W1 of the photoresist structures 120 in FIG.2H is significantly reduced compared to the width W1 of the photoresiststructures 120 of FIG. 2A. Correspondingly, the width W2 of the trenches128 in FIG. 2H is significantly increased with respect to the width W2of the trenches 128 in FIG. 2A.

The changes in in the widths W1 and W2 can be seen in FIGS. 2K and 2L.FIG. 2K is a top view of the wafer 106 at the processing stage of FIG.2A. The top view of FIG. 2K illustrates the photoresist structures 120extending in the Y dimension. The top view of FIG. 2K also illustratesthe trenches 128 between photoresist structures 120. FIG. 2L illustratesthe wafer 106 of the processing stage of FIG. 2H after the first andsecond ion bombardment steps have been performed on the sides 124 and126 of the photoresist structures 120. As can be seen in FIGS. 2K and2L, the width W1 of the photoresist structures 120 in the X dimension issignificantly smaller in FIG. 2L than in FIG. 2K. As can be seen inFIGS. 2K and 2L, the width W2 of the trenches 128 between photoresiststructures in the X dimension is significantly larger in FIG. 2L than inFIG. 2K. FIG. 2K illustrates the cut line A on which the cross-sectionof FIG. 2A is taken. FIG. 2L illustrates the cut line H on which thecross-section of FIG. 2H is taken.

In some embodiments the trenches 128 may initially be circular orotherwise rounded apertures when viewed from the top. After the ionbombardment steps, the circular or otherwise rounded apertures may beelongated in one or both of the X and Y directions.

Returning to the cross-sectional views, FIG. 2I corresponds to aprocessing stage after the view of FIG. 2H. In FIG. 2I trenches 130 havebeen opened in the substrate 122. The trenches 130 are opened by etchingprocess. The etching etches the portions of the substrate 122 exposed bythe photoresist structures 120. Accordingly, the photoresist structures120 act as a mask for patterning the substrate 122. The etching processcan be selected based on the material of the substrate 122. The etchingprocess can include wet etches, dry etches, or other types of etches.

In FIG. 2J, a metal has been deposited in the trenches 130, therebyforming metal lines 132. The metal can include tungsten, titanium,aluminum, copper, gold, the team nitride, tantalum nitride, or othertypes of metals. The photoresist material 120 has been removed and achemical mechanical planarization process has been performed to make thetop surface of the metal lines 132 even with the top surface of thesubstrate 122. The process of FIGS. 2I and 2J is just one example ofprocessing steps that can be performed using the fully patternedphotoresist structures 120 as a mask. Other processes can be performedwithout departing from the scope of the present disclosure.

The foregoing description of FIGS. 2A-2H described an embodiment inwhich the multistep ion bombardment process included changingbombardment angles between ion bombardment steps. However, othermultistep ion bombardment processes can be performed in accordance withprinciples of the present disclosure. Some of these processes will bedescribed below with reference to FIGS. 2B and 2D. However, these otherprocesses may use different process parameters and sequences than thosedescribed above. For example, other processes can use different angles,doses, energies or other parameters. Additionally, these other processesmay result in different shapes or profiles of the remaining photoresiststructures 120. The references to FIGS. 2B and 2D do not limit otherprocesses to the characteristics shown and described previously inrelation to FIGS. 2B and 2D.

In one embodiment, an ion bombardment process includes a first ionbombardment step and a second ion bombardment step. The energy of theions is changed between the first ion bombardment step and the secondion bombardment step. In this example, both ion bombardment steps areperformed with a sufficiently small bombardment angle that no shadowingoccurs in either step. Both ion bombardment steps can be visualized withreference to FIG. 2D in which the angle 82 is small enough to ensurethat no shadowing occurs. The difference between the first ionbombardment step in the current embodiment and the ion bombardment stepshown in FIG. 2D is that no material will have been removed and thecurrent embodiment prior to the first ion bombardment step. Angles otherthan 82 can be utilized in embodiments in which ion energy is changedbetween steps, without departing from the scope of the presentdisclosure.

The first ion bombardment step of a first side 124 is performed with afirst, relatively low ion energy. The entirety of the first side 124 isimpacted by the low-energy ions. The low ion energy results in little orno removal of photoresist material from the first side 124. However, aswill be described in more detail below, the low ion energy reduceshardening.

After the first ion bombardment step of the first side 124, a second ionbombardment step is performed on the first side 124. The second ionbombardment step is at the same angle as the first ion bombardment step.The second ion bombardment step includes a second ion energy. The secondion energy is higher than the first ion energy. The result of the secondion bombardment step is the removal of photoresist material from theentirety of the first side 124, both upper and lower portions. This mayresult in a flatter profile of the first side 124 than is shown in FIG.2E.

In one embodiment, the photoresist is a polymer material includingpolymer chains. Hardening of the polymer material occurs when highenergy ions impact the polymer and cause a fusing of adjacent polymerchains. This fusing hardens the polymer and makes it more difficult toremove the polymer. However, lower energy ions do not have sufficientenergy to fuse adjacent polymer chains, but cause loosening or breakingof the polymer chains. The loosened polymer chains do not fuse whenbombarded with high energy ions. Instead, the loosened polymer chainsare destroyed and removed by the high energy ions. Accordingly, if lowerenergy ions are first used to loosen the polymer chains, then subsequentbombardment by high energy ions will removed the loosened polymer chainswithout hardening them.

In one embodiment, the first ion energy is between 0.5 keV and 2.0 keV.If the first ion energy is higher than this range, then hardeningeffects may occur. If the first ion energy is lower than this range,then there may be substantially no effect on the photoresist. The secondion energy is between 4 keV and 8 keV. If the second ion energy is lowerthan this range, then little photoresist material may be removed fromthe first side 124. If the second ion energy is greater then this range,then too much photoresist material may be removed from the first side124. In one example, the first ion energy is 1.0 keV and the second ionenergy is 6 keV. Other ion energies can be utilized for the first andsecond ion bombardment steps without departing from the scope of thepresent disclosure. The duration of the first and second ion bombardmentsteps may be the same or different from each other.

After the first and second ion bombardment steps have been performed onthe first side 124 at the respective low and high ion energies, thewafer 106 is rotated 180° as described in relation to FIG. 2F. The lowand high energy ion bombardment steps are then performed on the secondside 126.

In one embodiment, the first low-energy ion bombardment step may have afirst ion dose and the second high energy ion bombardment step may havea second ion dose different than the first ion dose. The second ion dosemay be higher than the first ion dose. In one example, the firstlow-energy dose of ions is between 1E14 and 2E15 ions. If the firstlow-energy dose of ions is lower than this range, then there may belittle effect on the photoresist structures 122. If the first low-energydose of ions is higher than this range, then hardening may occur. In oneexample, the second dose of ions is between 2E15 ions and 1E16 ions. Ifthe second high energy dose of ions is lower than this range, thenlittle photoresist material may be removed. If the second high-energydose of ions is greater than this range, then too much photoresistmaterial may be removed. Other doses can be utilized without departingfrom the scope of the present disclosure.

In another embodiment in which the ion bombardment angle changes betweenthe first and second ion bombardment steps, as shown in FIGS. 2B and 2D,the ion energies are also changed between the first and second ionbombardment steps. In particular, in the first high incident angle ionbombardment step, the ions may have a low ion energy as described above.In the second low incident angle ion bombardment step, the ions may havea high energy as described above.

More than two ion bombardment steps may be performed on each side 124and 126. For example, in one embodiment, three ion bombardment steps maybe performed on each side 124 and 126. The first ion bombardment step isperformed at the high incident angle as shown in FIG. 2B. The first ionbombardment step has a low ion energy. The second ion bombardment stepis performed at the low incident angle as shown in FIG. 2D. The secondion bombardment step is also performed with the low ion energy. A thirdion bombardment step is performed at the low incident angle as shown inFIG. 2D with the high ion energy.

In another embodiment, three ion bombardment steps may be performed oneach side 124 and 126. The first ion bombardment step is performed atthe high incident angle as shown in FIG. 2B. The first ion bombardmentstep has a low ion energy. The second ion bombardment step is performedat the high incident angle as shown in FIG. 2B. The second ionbombardment step is performed with the high ion energy. A third ionbombardment step is performed at the low incident angle as shown in FIG.2D with the high ion energy.

In another embodiment, three or more ion bombardment steps may beperformed on each side 124 and 126. Each of the three or more ionbombardment steps may have a different bombardment angle. In anotherembodiment, each of the three or more ion bombardment steps may have adifferent bombardment energy.

FIG. 3 is a graph 300 illustrating photoresist removal for various ionbombardment processes versus trench with. Accordingly, the X-axiscorresponds to the initial width W2 of the trenches as shown in FIG. 2A.The Y-axis corresponds to the change in the width W1 of the photoresiststructures 120 after the ion bombardment processes have been performedon both the first side 124 and the second side 126. The line 302corresponds to a multistep process in which the first ion bombardmentstep is a high incident angle ion bombardment step and the second ionbombardment step is a low incident angle ion bombardment step. The line304 corresponds to a single step process in which the ion bombardment isperformed only with the high incident angle. The line 306 corresponds toa multistep process in which the first ion bombardment step is a lowincident angle ion bombardment step and the second ion bombardment stepis a high incident angle ion bombardment step. The line 306 correspondsto a single step process in which the ion bombardment is performed onlywith the low incident angle.

The grouping 310 identifies the data point for each of the lines forwhich the initial width W2 is the lowest. The shadowing effect in thiscase is strongest because the photoresist structures 120 are relativelyclose together. As can be seen, the line 302 always results in a removalof a greater amount of photoresist material compared to other processes.Accordingly, a multi-step process in which a high incident angle isfirst used and a low incident angle is then used (as shown in FIGS.2A-2H) can be very beneficial.

Though not shown in the Figures, a process in which a first ionbombardment step includes a low energy and high-dose while the secondion bombardment step includes a high-energy and low dose provides agreater removal of photoresist material than other combinations ofenergies and doses.

FIGS. 4A-4D are top views of integrated circuits 106 including elongatedtrenches 128 formed in photoresist, according to some embodiments. FIGS.4A-4D illustrate relative widths in the X direction of the trenches 128for various ion bombardment energies and doses. In FIG. 4A, ionbombardment has not been performed after initial formation of thetrenches 128 in the photoresist 120.

In FIG. 4B, a single ion bombardment step has been performed with ionenergy of 6 keV and a dose of 4E15 ions. The width of the trenches 128in the X direction is wider than the width of the trenches 128 of FIG.4A.

In FIG. 4C, a two-step ion bombardment processes been performed. Thefirst ion bombardment step has an energy of 6 keV and a dose of 1E15.The second ion bombardment step has an energy of 1 keV and a dose of3E15. The trenches 128 of FIG. 4C are wider than the trenches 128 ofFIG. 4B. Accordingly, the two-step ion bombardment process of FIG. 4Cresults in the removal of more photoresist than the single step processof FIG. 4B.

In FIG. 4D, a two-step ion bombardment process has been performed. Thefirst ion bombardment step has an energy of 1 keV and a dose of 3E15.The second ion bombardment step has an energy of 6 keV and a dose of1E15. The trenches 128 of FIG. 4D are wider in the X direction than thetrenches 128 of FIG. 4C. Accordingly, the two-step ion bombardmentprocess of FIG. 4D in which low-energy ions and the high-dose are usedin the first step and high-energy ions with a low dose are used in thesecond step results in removal of more photoresist than the two-stepprocess of FIG. 4C in which high-energy ions with a low dose are used inthe first step and low-energy ions with a high dose are used in thesecond step.

FIGS. 4A-4D are top views of integrated circuits 106 including elongatedtrenches 128 formed in photoresist, according to some embodiment. FIGS.4A-4D illustrate relative widths in the X direction of the trenches 128for various ion bombardment energies and doses. In FIG. 4A, ionbombardment has not been performed after initial formation of thetrenches 128 in the photoresist 120.

FIGS. 5A-5D are top views of integrated circuits 106 including nearlycircular trenches 128 formed in photoresist 120, according to someembodiments. FIGS. 5A-5D utilize the processes described in relation toFIGS. 4A-4D. In particular, in FIG. 5A no ion bombardment processes beenperformed. In FIG. 5B, the same ion bombardment process as FIG. 4B hasbeen performed. In FIG. 5C, the same ion bombardment process as FIG. 4Chas been performed. In FIG. 5D, the same ion bombardment process of FIG.4D has been performed. The width of the trenches in the X direction getprogressively wider from FIG. 5A to 5D, similar to FIGS. 4A-4D. FIG. 6is a perspective view of a wafer 106, according to one embodiment. Thewafer 106 includes a substrate 120. Photoresist 120 has been depositedon the substrate 120 and trenches 128 have been formed in thephotoresist 120 by a photolithography process. In FIG. 6, an ionbombardment step is performed. Ions 129 bombard the photoresist 120. Theion bombardment step can have the characteristics or parameters of anyof the ion bombardment steps described previously. The ion bombardmentstep may be a first ion bombardment step, the second ion bombardmentstep, or another ion bombardment step in ion bombardment process. Theresult of the ion bombardment process is that the trenches 128 arewidened. As can be seen in FIG. 6, in the X direction, the trenches 128are somewhat rounded. The trenches 128 shown in FIGS. 2A-2K may also berounded in a similar manner.

FIG. 7 is a block diagram of the control system 112 of FIG. 1. Thecontrol system 112 includes processing resources 140, memory resources142, and communication resources 144. The processing resources 140 caninclude one or more processors. The memory resources 142 can include oneor more memories that include software instructions for controlling theion source 108 and other components of the semiconductor process system100 of FIG. 1. When the processors execute the software instructionsstored in the memories, the control system 112 performs a process forcontrolling the semiconductor process system. The process can includeperforming the multiple ion bombardment steps and wafer rotation asdescribed previously.

The control system 112 also includes communication resources 144. Thecommunication resources can include wireless transceivers, wiredconnections, and circuitry for outputting and receiving signals via thewireless transceivers and or wired connections. Accordingly, thecommunication resources 144 can relay commands for controlling thecomponents of the semiconductor process system 100.

FIG. 8 is a flow diagram of a method 800 for performing a semiconductorprocess, according to one embodiment. The method 800 can utilize thesystems, structures, components, and processes described in relation toFIGS. 1-6. At 802, the method includes depositing photoresist on asubstrate one example of a substrate is the substrate 122 of FIG. 2A. At804, the method 800 includes forming a trench in the photoresist oneexample of a trench is the trench 128 of FIG. 2A. At 806, the method 800includes widening the trench by bombarding a first side of the trenchwith ions from a first angle. One example of a first side is the side124 of the photoresist structure 120 of FIG. 2B. At 808, the method 800includes widening the trench by bombarding the first side of the trenchwith ions from a second angle different from the first angle.

FIG. 9 is a flow diagram of a method 900 for performing a semiconductorprocess, according to one embodiment. The method 900 can utilize thesystems, structures, components, and processes described in relation toFIGS. 1-5. At 902, the method 900 includes depositing photoresist on asubstrate. One example of a substrate is the substrate 122 of FIG. 2A.At 904, the method 900 includes forming a photoresist structure bypatterning the photoresist. One example of a photoresist structure isthe photoresist structure 120 of FIG. 2A. At 906, the method 900includes reducing a width of the photoresist structure by bombarding afirst side of the photoresist structure with ions having a first energy.One example of a first side is the side 124 of the photoresist structure122 of FIG. 2B. At 906, the method 900 includes bombarding the firstside of the photoresist structure with ions having a second energydifferent than the first energy after bombarding the first side of thephotoresist structure with ions having the first energy.

In one embodiment, a method includes depositing photoresist on asubstrate, forming a trench in the photoresist, and widening the trenchby bombarding a first side of the trench with ions from a first angleand bombarding the first side of the trench with ions from a secondangle different from the first angle.

In one embodiment, a method includes depositing photoresist on asubstrate and forming a photoresist structure by patterning thephotoresist. The method includes reducing a width of the photoresiststructure by bombarding a first side of the photoresist structure withions having a first energy and bombarding the first side of thephotoresist structure with ions having a second energy different thanthe first energy after bombarding the first side of the photoresiststructure with ions having the first energy.

In one embodiment, a system includes a semiconductor process chamber, awafer support configured to support a wafer in the semiconductor processchamber, an ion source positioned to bombard the wafer with ions, and acontrol system coupled to the ion source. The control system includes atleast one processor and at least one memory coupled to the at least oneprocessor, the at least one memory having stored therein, instructionswhich, when executed by the one or more processors, cause the ion sourceto bombard, from a first angle, a side of a photoresist structure on awafer in a first ion bombardment step, to bombard, from the first angle,the side of the photoresist structure on a wafer in second ionbombardment step, and to bombard, from a second angle different than thefirst angle, the side of the photoresist structure in a third ionbombardment step.

The various embodiments described above can be combined to providefurther embodiments. Aspects of the embodiments can be modified, ifnecessary, to employ concepts of the various patents, applications andpublications to provide yet further embodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

1. A method, comprising: depositing photoresist on a substrate; forminga trench in the photoresist; widening the trench by: bombarding a firstside of the trench with ions from a first angle; and bombarding thefirst side of the trench with ions from a second angle different fromthe first angle.
 2. The method of claim 1, further comprising wideningthe trench by: bombarding a second side of the trench with ions from thefirst angle; and bombarding the second side of the trench with ions froma second angle different from the first angle.
 3. The method of claim 2,further comprising rotating the substrate 180 degrees between bombardingthe first side and the second side.
 4. The method of claim 1, whereinthe first angle is greater relative to vertical than is the secondangle.
 5. The method of claim 4, wherein the first angle is between 55degrees and 65 degrees relative to vertical, wherein the second angle isbetween 40 degrees and 50 degrees relative to vertical.
 6. The method ofclaim 5, wherein the first angle is 60 degrees and the second angle is45 degrees.
 7. The method of claim 1, wherein bombarding the first sideof the trench with ions from the first angle includes bombarding thefirst side of the trench with ions having a first energy, whereinbombarding the first side of the trench with ions from the first angleincludes bombarding the first side of the trench with ions having asecond energy greater than the first energy.
 8. The method of claim 7,wherein the first energy is between 0.5 keV and 2 keV, wherein thesecond energy is between 4 keV and 8 keV.
 9. The method of claim 1,wherein bombarding the first side of the trench with ions from the firstangle includes bombarding the first side of the trench with a first doseof ions, wherein bombarding the first side of the trench with ions fromthe first angle includes bombarding the first side of the trench with asecond dose of ions greater than the first dose.
 10. The method of claim1, further comprising, after widening the trench: etching the substrateusing the photoresist as a mask; and depositing a metal in thesubstrate.
 11. The method of claim 1, wherein the ions are argon ions.12. A method, comprising: depositing photoresist on a substrate; forminga photoresist structure by patterning the photoresist; reducing a widthof the photoresist structure by: bombarding a first side of thephotoresist structure with ions having a first energy; and bombardingthe first side of the photoresist structure with ions having a secondenergy different than the first energy after bombarding the first sideof the photoresist structure with ions having the first energy.
 13. Themethod of claim 12, further comprising reducing the width of thephotoresist structure by: bombarding a second side of the photoresiststructure with ions having the first energy; and bombarding the secondside of the photoresist structure with ions having the second energyafter bombarding the second side of the photoresist structure with ionshaving the first energy.
 14. The method of claim 13, wherein the firstenergy is between 0.5 keV and 2 keV, wherein the second energy isbetween 4 keV and 8 keV.
 15. The method of claim 12, wherein bombardingthe first side of the photoresist structure with ions from the firstenergy includes bombarding the first side of the photoresist structurewith a first dose of ions, wherein bombarding the first side of thephotoresist structure with ions from the first energy includesbombarding the first side of the photoresist structure with a seconddose of ions less than the first dose.
 16. A system, comprising: asemiconductor process chamber; a wafer support configured to support awafer in the semiconductor process chamber; an ion source positioned tobombard the wafer with ions; and a control system coupled to the ionsource and including: at least one processor; and at least one memorycoupled to the at least one processor, the at least one memory havingstored therein, instructions which, when executed by the one or moreprocessors, cause the ion source to bombard, from a first angle, a sideof a photoresist structure on a wafer in a first ion bombardment step,to bombard, from the first angle, the side of the photoresist structurein second ion bombardment step, and to bombard, from a second angledifferent than the first angle, the side of the photoresist structure ina third ion bombardment step.
 17. The system of claim 16, wherein thefirst and second ion bombardment steps have a same energy.
 18. Thesystem of claim 17, wherein the third ion bombardment step has a secondenergy higher than the first energy.
 19. The system of claim 16, whereinthe second and third ion bombardment steps have a same first energy. 20.The system of claim 17, wherein the first ion bombardment step has asecond energy lower than the first energy.